1. Field of the Invention
The present invention relates to a cylinder head having an integrally formed port-exhaust manifold assembly, more particularly, the present invention relates to a cylinder head having an integrally formed port-exhaust manifold assembly in which an exhaust port is extended to function as an exhaust manifold.
2. Description of Related Art
Generally, the exhaust manifold has developed as another component. The exhaust manifold is independently manufactured and then mounted on the cylinder head.
Accordingly, it is an important factor in that it may largely affect an engine on an entire performance and durability and it may thermally deteriorate a vehicle.
The vehicle must have a space for accommodating such an exhaust manifold in an engine compartment. Also, the vehicle must have a sufficient space for separating peripheral components from the exhaust manifold not to thermally deteriorate the same.
Meanwhile, such an exhaust manifold requests that a catalyzing means is enough near to rapidly activate the exhaust manifold. Accordingly, it is desired that the exhaust manifold are compactly disposed in the engine.
However, in case of a V6 engine in which six cylinders are disposed in a V-shaped pattern such that each three cylinders are arranged at an angle of 60° at left and right sides based on a center line, it is difficult to satisfy all of two opposed conditions in which one is providing a sufficient space for thermally insolating the exhaust manifold and a thermal-insulting means to be additionally mounted in a cylinder head and the other is providing a close space for the catalyzing means to be near to the exhaust manifold.
In order to satisfy all of two opposed space conditions, the shape of the exhaust manifold cannot help being rapidly changed.
Such a rapid shape change of the exhaust manifold may provide a loss of a performance, a further distance from the catalyzing means, and a loss of the thermal durability and accordingly, a thermal stress is converged on to generate a crack.
In addition, in order to make an engine compact, Japan Patent No. 2709815 discloses that the exhaust manifold is integrally formed with the exhaust port in a cylinder head of a series three cylinder engine.
With such a structure, for example, in case of a series four cylinder engine, it has a merit in that the compact engine may be achieved because the function of the exhaust manifold is performed in the cylinder head.
However, it has a drawback in that a torque is decreased at a low velocity and at a middle velocity since the pulsatory motion interference according to an increase of the number of the cylinder heads is generated on exhausting, which is an important characteristic of the engine.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.